A control device for an internal combustion engine controls parts of the internal combustion engine, such as an injector, and adjusts opening/closing timing of an injector on which an injection timing of fuel and an amount of the fuel are determined. The control unit of the control device determines the fuel injection timing and the amount of the fuel based on the stepped value of an accelerator and a detected result of the operation condition of the internal combustion engine. In order to burn the fuel properly, the amount of gas is controlled by a gas adjusting means such as an intake throttle valve and an EGR valve to make a mixture gas with the fuel.
The control of the gas adjusting means is executed by detecting the condition amount of the engine condition which is varied according to the operation amount of the gas adjusting means, and establishing the operation amount of the gas adjusting means in such manner that the detected condition amount is consistent with the target value. The target value of the condition amount is established in such a manner that an emission level is restricted under a predetermined level. In the control unit, the relationship between the control condition including a required torque and a target value of the condition amount is stored in a map. An exhaust oxygen concentration, an amount of fresh-air, an intake oxygen concentration, and an intake air pressure are used as the condition amount.
To reduce the emission, a high-pressure injection and a multi injection is developing. However, these injections have following problems. That is, because the higher-pressure injection causes a shorter period of injection, the error of injection timing dominates in the error of the injected fuel amount. In the multi injection, a sum of injected fuel amount from each injector corresponds to an injected fuel amount in a power stroke. Since the number of injection is increased, the error in each injector is accumulated. As a result, the target condition amount corresponding to the required torque becomes different from a condition amount corresponding to an actually generated torque, by which the emission deteriorates. JP-2001-90580 A discloses a system in which a time lag from the time of activating the injector to the time of opening the injector is derived from a learning injection, then the time lag is reflected to a length and output timing of a driving pulse which controls the fuel injection period.
The system disclosed in JP-2001-90580 A 1 is desirable in averaging a characteristic of the injector. However, an operational dispersion of the injector is not concerned. FIG. 19 shows a characteristic of a target fresh-air amount relative to the required torque. The target fresh-air amount GA_TRG is not constant and varies according to the required torque T. A line fGA (NE, T) represents the target fresh-air amount GA_TRG in the engine condition (NE, T). Thus, when the required torque T0 disperses in a range in which the actual injected fuel amount generates the torque T0±ΔT, the proper target fresh-air amount GA_TRG deviates from GA_TRG0 (=fGA (NE, T0)) according to the dispersion of the injected fuel amount. If the deviation ΔGA_TRG uniformly varies, the deviation ΔGA_TRG can be estimated as |fGA(NE, T0+ΔT)−fGA(NE, T0−ΔT)|. The fresh-air amount can be converted in to EGR ratio as shown in FIG. 20. If the fresh-air amount which is necessary for the actual injected fuel amount deviates from GA_TRG0, a deviation AEGR is generated between the EGR ratio EGR0 converted by setting the target fresh-air amount as GA_TRG0 and a EGR ratio suitable for the actual injected fuel amount. As the result, the emission level can be deteriorated rather than the predetermined level.